It also might not be related to COW and instead be something in the regex engine that is specific to windows.

I wouldn't yet assume that it doesn't afflict Linux.
Sure, there's nothing much in the figures that hippo choroba posted earlier, but I wonder if the same thing might become evident on Linux if "1e6" is increased to "2e6" or beyond.

It's probably worth flagging with p5p

Probably, yes.
The 5.38.0 perlvar docs still warn about the potential performance hits of using $&, but then they also say (regarding $`, $& and $') 
    In Perl 5.20.0 a new copy-on-write system was enabled by default, 
+which
    finally fixes most of the performance issues with these three vari
+ables,
    and makes them safe to use anywhere.

[download]
But note that it says "most of the performance issues".
And I'm still a bit curious to know whether a perl-5.38.0 windows perl built without COW would suffer the same slowdown.

Cheers,
Rob

In reply to Re^4: Substitution unexpectedly very slow, in Strawberry by syphilis
in thread Substitution unexpectedly very slow, in Strawberry by Anonymous Monk

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